Some minor changes and playing about

Core/Cpu/Z80.cs

@@ -1,5 +1,6 @@
 using System;
 using Core.Interfaces;
+using Core.Io;
 
 namespace Core.Cpu
 {
@@ -38,12 +39,12 @@ namespace Core.Cpu
 
         // The Memory Bus
         private readonly IMemory _memory;
-        private readonly IIoBus _ioBus;
+        private readonly IO_Bus _simpleIoBus;
 
-        public Z80(IMemory memory, IIoBus ioBus)
+        public Z80(IMemory memory, IO_Bus ioBus)
         {
             _memory = memory;
-            _ioBus = ioBus;
+            _simpleIoBus = ioBus;
             Reset();            
         }
 
@@ -122,15 +123,7 @@ namespace Core.Cpu
         // Placeholder for your hardware I/O
         private byte ReadPort(ushort portAddress)
         {
-            // If the port is 0xFE, the ROM is asking for keyboard/tape/ULA data!
-            // For now, we will return 0xFF (meaning "No keys are currently pressed")
-            if ((portAddress & 0xFF) == 0xFE)
-            {
-                return 0xFF;
-            }
-
-            // Default floating bus return
-            return 0xFF;
+            return _simpleIoBus.ReadPort(portAddress);
         }
 
         public int Step()
@@ -1086,7 +1079,7 @@ namespace Core.Cpu
                     // The Z80 puts 'A' on the top 8 bits, and 'n' on the bottom 8 bits of the port address
                     ushort portAddress = (ushort)((AF.High << 8) | portOffset);
 
-                    _ioBus.Write(portAddress, AF.High);
+                    _simpleIoBus.WritePort(portAddress, AF.High);
 
                     return 11;
                 case 0xd5: //push bc

Core/Io/IO_Bus.cs

@@ -0,0 +1,43 @@
+using System.Diagnostics;
+using Core.Interfaces;
+
+namespace Core.Io
+{
+    public class IO_Bus
+{
+    // 8 rows representing the Spectrum keyboard matrix. Default to 0xFF (unpressed).
+    public byte[] KeyboardRows = new byte[8] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
+
+    public byte ReadPort(ushort portAddress)
+    {
+        // The Spectrum ULA responds to any even port address (where the lowest bit is 0)
+        if ((portAddress & 0x01) == 0)
+        {
+            byte highByte = (byte)(portAddress >> 8); // The B register!
+            byte result = 0xFF; // Start assuming no keys are pressed
+
+            // The ROM pulls a specific bit low (0) in the high byte to request a row.
+            // Sometimes it pulls multiple bits low to scan multiple rows at once, so we AND the results.
+            if ((highByte & 0x01) == 0) result &= KeyboardRows[0]; // 0xFE: CAPS, Z, X, C, V
+            if ((highByte & 0x02) == 0) result &= KeyboardRows[1]; // 0xFD: A, S, D, F, G
+            if ((highByte & 0x04) == 0) result &= KeyboardRows[2]; // 0xFB: Q, W, E, R, T
+            if ((highByte & 0x08) == 0) result &= KeyboardRows[3]; // 0xF7: 1, 2, 3, 4, 5
+            if ((highByte & 0x10) == 0) result &= KeyboardRows[4]; // 0xEF: 0, 9, 8, 7, 6
+            if ((highByte & 0x20) == 0) result &= KeyboardRows[5]; // 0xDF: P, O, I, U, Y
+            if ((highByte & 0x40) == 0) result &= KeyboardRows[6]; // 0xBF: ENTER, L, K, J, H
+            if ((highByte & 0x80) == 0) result &= KeyboardRows[7]; // 0x7F: SPACE, SYM, M, N, B
+
+            // The top 3 bits (5, 6, 7) are unused by the keyboard and usually return 1 on a real Spectrum
+            return (byte)(result | 0xE0);
+        }
+
+        // Return 0xFF for unhandled ports
+        return 0xFF; 
+    }
+
+    public void WritePort(ushort portAddress, byte portValue)
+        {
+
+        }
+}
+}

Core/Io/SimpleIoBus.cs

@@ -1,20 +0,0 @@
-using System.Diagnostics;
-using Core.Interfaces;
-
-namespace Core.Io
-{
-    public class SimpleIoBus : IIoBus
-    {
-        public byte Read(ushort port)
-        {
-            // If the CPU reads an unconnected port, the Z80 usually sees 0xFF
-            return 0xFF;
-        }
-
-        public void Write(ushort port, byte value)
-        {
-            // For now, let's just log it to the Visual Studio Output window
-            Debug.WriteLine($"Hardware I/O Write -> Port: 0x{port:X4}, Value: 0x{value:X2}");
-        }
-    }
-}

Core/Memory/MemoryBus.cs

@@ -35,12 +35,20 @@ namespace Core.Memory
         public void CrapRAMData()
         {
             Random random = new Random();
-            for (int i = 0x4000; i < 0x5AFF; i++)
+            for (int i = 0x4000; i < 0xFFFF; i++)
             {
                 _memory[i] = (byte)random.Next(0x00, 0xFF);
             }
         }
 
+        public void CleanRAMData()
+        {            
+            for (int i = 0x4000; i < 0xFFFF; i++)
+            {
+                _memory[i] = 0x00;
+            }
+        }
+
         // Load the ROM file
         public void LoadRom(byte[] romData)
         {